The 2017 season concluded on 20 November with Grigor Dimitrov winning the ATP Finals in London and all the top players are currently on holiday before they return to competitive action at the start of the New Year as they begin their preparations for the first Grand Slam of the year in Australia.
Federer will represent Switzerland at the Hopman Cup at the start of the year and will be joined by Alexander Zverev and ATP Finals runner-up David Goffin.
Djokovic will begin his campaign in Doha alongside Dominic Thiem and Pablo Carreno Busta.
Nadal and Murray, meanwhile, lead an all-star cast at the Brisbane International as they will be joined by Milos Raonic, Kei Nishikori and new world number three Dimitrov. Marin Cilic and US Open finalist Kevin Anderson will be in India for the Maharashtra Open in Pune.
Among the players beginning their season in the first week of 2018, the likes of Djokovic, Murray, Raonic and Nishikori are returning from long-term injury absences. Their rankings have dropped since they ended their 2017 season early and it is likely to be a mixed draw at the first Grand Slam in Melbourne, similar to this year when Federer and Nadal were seeded 17 and nine, respectively.
Nadal and Djokovic, meanwhile, are slated to return before the official start of the 2018 season as they have confirmed their participation at the Mubadala World Tennis Championship in Abu Dhabi at the end of the year. They will be joined by Thiem, Raonic, Carreno Busta and Stan Wawrinka in the Middle East for the tournament that runs from 28-30 December.